1. Field of the Invention
The present invention is in the field of automotive mechanics and specifically relates to a tool for installing valve locks on a valve stem. The valve lock removably secures a valve retainer to the valve stem. The tool typically would be used by an automobile mechanic or by an engine reconditioner.
2. The Prior Art
During the compression and expansion cycles, the valves of a conventional internal combustion engine are forced shut by the high pressure within the cylinder. To implement the intake and exhaust cycles, the valves must be opened at appropriate times, and this is usually accomplished by the use of a cam that pushes against the end of the valve stem, thereby forcing the head of the valve into the combustion chamber. To assure positive operation, a valve spring urges the valve to its closed position, and the cam must overcome the urging of the valve spring to open the valve. Typically, the valve spring is a compression spring. One end of the compression spring bears against a stationary part of the engine, and the other end of the spring bears against a valve spring retainer that is removably secured to the valve stem by a valve lock. Were it not for the valve lock, the compressive force of the valve spring would push the retainer off the end of the valve stem. The retainer must be removably secured to the valve stem to permit assembly and dis-assembly of the valve.
In theory, a nut and washer would suffice to secure the retainer to the valve stem. However, after nearly a century of experience, a specialized type of valve lock is almost universally used. The retainer has a tapered central bore that opens toward the end of the valve stem. The valve stem has an end portion that includes a circumferential groove. The valve lock is a tapered split collar that has an inwardly facing ridge. The ridge engages the circumferential groove of the valve stem and is held in engagement by the taper of the central tapered bore of the retainer. The valve lock is thus jammed between the circumferential groove on the valve stem and the tapered central bore of the retainer, which is urged toward the end of the valve stem by the valve spring.
Although this way of securing the retainer to the valve stem is simple and effective in use, it has proven to be very challenging for most mechanics to take apart and reassemble, which must be done when the valves are ground or the engine is reconditioned.
Part of the difficulty is that the retainer must be drawn back, away from the end of the valve stem against the urging of the valve spring, to expose the valve locks. In contemporary engines, the force exerted by the valve spring is in the range of 60 to 90 pounds, and mere finger pressure generally is not adequate. Another part of the difficulty is that the valve locks are rather small in comparison to the valve stem and are difficult to manipulate. To make matters worse, the valve spring and the retainer are frequently located in a poorly-illuminated and fairly close-fitting recess, which makes the parts somewhat inaccessible.
Large console-type machines are commercially available, but they merely compress the valve springs. They occupy valuable floor space in the shop, and have a high initial cost. It appears that a need exists for a hand tool to facilitate the installing of valve locks.